JPS6180800A - Radiation light irradiator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an apparatus for irradiating an object to be irradiated, such as a semiconductor wafer, using synchrotron orbital synchrotron radiation.

[Background of the invention]

As schematically shown in Figure 24, synchrotron orbital synchrotron radiation is an electromagnetic wave that is emitted when the trajectory of electrons near the speed of light is bent by a magnetic field H, and has strong directivity in the tangential direction of the orbit. Therefore, it has various uses, and is very useful as a radiation source for transferring fine patterns of electronic parts, for example.

When performing irradiation for exposure using this synchrotron radiation, the 24th
As shown in the figure, a sufficiently uniform exposure can be obtained in the horizontal direction (left and right in this figure), but a spread of only about 1/r radian can be obtained in the vertical direction (Z direction in this figure). However, γ is the ratio between the electron energy and the rest mass of the electron, and when the electron energy is 500 MeV, r = 10
It is 00. Therefore, in this case, the vertical radiation angle is about 1 milliradian, and an exposure width of only 5 strips can be obtained at a point 5 meters from the light emitting point. On the other hand, in the case of wafers as objects to be irradiated, they usually have a diameter of 10α or more, and when transferring fine patterns onto these objects, the emitted light beam must be expanded (the diameter of the light beam should be increased) in order to obtain a large exposure area. (enlargement) is required.

Conventional methods for expanding synchrotron radiation include optically expanding the synchrotron radiation beam and changing the trajectory of stored electrons. As a method of optically expanding the radiation beam, there is a method of reflecting the radiation with a swinging mirror. However, it has the disadvantage that the exposure time is long because the reflection coefficient of the mirror is low.

One way to change the trajectory of stored electrons is to swing the trajectory up and down using a weak transverse magnetic field from a steering magnet. However, with this method, if a magnetic field with a magnetic field strength above a certain level is applied, the electron beam will be lost and the size of the synchrotron radiation cannot be sufficiently expanded. Another drawback is that the electron beam tends to become unstable due to the application of a dynamic magnetic field. Furthermore, since this method mainly changes the inclination of the orbit of the electron beam to change the direction of emission of the synchrotron radiation, the exposed area cannot be obtained unless the distance is sufficiently far. For example, the maximum
The i exposure width is about 3 strokes at the 10m point, but at the 5m point,
Then, it becomes about 1.7cn1. However, by enlarging the size of the electron beam itself, the exposure area can be increased without moving away from the emission point, and if combined with a method of changing the emission direction of the synchrotron radiation by tilting the orbit, a wide exposure area can be obtained. Therefore, in order to effectively utilize this synchrotron orbital synchrotron radiation in industrial production, it is important to expand its beam size.

For information on how to expand the beam size of synchrotron orbital synchrotron radiation, please refer to Magazine 6 Japanese Science and Technology "'84 Ultrafine Fabrication Special Feature" (Published by Japan Science and Technology Foundation 25-2)
28-July, August), Mr. Nobuo Atota's 7th Generation Favorite Phosphorography Technology" is detailed. According to this method, in addition to the magnet used to deflect the electron beam, the electron beam is expanded. Therefore, four or more converging quadrupole magnets are required, which makes the entire device complicated and large, and has the disadvantage that adjustment is complicated.

On the other hand, by making the electron beam deflection magnet have a magnetic field strength change in the radial direction, it can be given both deflection and convergence functions, or both deflection and divergence functions, and a strong Convergent synchrotrons are also known. In this device, the beam size can be maximized with the deflection magnet section, but there is a problem that it cannot be used as a storage ring because the imaging in the radial direction diverges.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and provides a synchrotron radiation irradiation device that can expand the size of synchrotron radiation emitted from an electron beam, has a simple structure, and can be configured in a small size. This is what we are trying to provide.

[Summary of the invention]

In order to achieve the above object, the synchrotron radiation irradiation device of the present invention includes a high-frequency acceleration cavity for accelerating electrons, a magnet for deflecting the electron beam,
an electron storage ring having a converging magnet, a diverging magnet, and a vacuum chamber, an installation station for installing an object to be irradiated, and a beam line that guides synchrotron radiation from a synchrotron radiation generation point of the electron storage ring to an object to be irradiated; In a synchrotron radiation irradiation device equipped with a synchrotron radiation device, the electron beam deflection magnet is provided with a part that performs the deflection and convergence action of the electron beam, and a part that performs the deflection action and the divergence action of the electron beam in the other part. The present invention is characterized in that it has a portion that performs the following functions, and the other portions are configured to function only to deflect the electron beam, thereby omitting the installation of a magnet dedicated to convergence and a magnet dedicated to divergence.

[Embodiments of the invention]

Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 8.

This embodiment (see FIG. 2) is an example of a synchrotron radiation irradiation device configured to irradiate a semiconductor wafer 531 with light emitted by introducing electrons into a storage ring 510 that stores electrons accelerated by an accelerator 500. be.

The radiation device of this embodiment includes an accelerator 500 that accelerates electrons,
The storage ring installation station 530 stores the accelerated electrons.

tfit'), as shown in FIG.
A septum magnet 610 that deflects the electrons from 00 and guides them into the storage ring 510, a kicker magnet 6201 that distorts the electron trajectory and makes it easier to enter, a high frequency acceleration cavity 6301 that accelerates the electrons, a beam monitor 640 that monitors the position of the electron beam, It consists of a vacuum pump 660 that makes the vacuum chamber 650 of the ring a high vacuum.

As shown in FIGS. 7 and 8, if there is a vacuum leak at the absorber 7001 installation station 530, etc., which blocks synchrotron radiation, the beam line 520 will prevent gas from entering the high vacuum ring 650 (FIG. 3). High-speed shutoff pulp 710 that shuts off between the ring side and the station side to prevent intrusion
When electrons are injected from the accelerator 500 into the storage ring 510, a device such as a gun starter 720 is used to prevent radiation from entering the installation station.

In the installation x+--y''', an X1-ray mask 800, an X-ray sensitive Xi resist 810, a semiconductor wafer 820, etc. are installed as shown in Figure 's9'.

The electron ■ is accelerated to a predetermined energy by an accelerator (
(FIG. 3), is incident on the storage ring 510. The incident electrons do not vibrate around a fixed orbit 400 determined by the deflecting and focusing magnet 600 and continue to rotate within the &'MIJ ring. This central orbit is called a closed orbit 400, and the vibrational motion around this orbit is called betatron oscillation. This vibrational motion can be decomposed into vibrations in the vertical direction 2 and horizontal direction X, which causes the electron beam to have a certain size. This betatron oscillation is caused by the deflection and focusing electromagnet 600 (Figures 3 and 7).
The loss width is adjusted and an appropriate beam size is obtained.

Electrons from the accelerator 500 are deflected by a deflection and focusing electromagnet 600 (third
It is bent by a septum magnet 610 provided in the straight line between the rings (see Figure) and placed on a closed track 400 within the ring. At this time, the closed track 650 is bent by the kicker magnet 620 as shown by the broken line 400' in FIG. If the electrons entered the storage ring go around the ring several times, they will collide with the septum magnet 610 again, so the kicker magnet 620 is lowered and the closed orbit 650 returns to the original orbit 400.
Return to. While orbiting within the ring, the electrons are subjected to accelerated motion by the deflection magnet section 600 and emit light. This light is called synchrotron radiation and has a wide spectral distribution. In order to emit this synchrotron radiation, the betatron oscillations are attenuated to a certain beam size. In this way, after a certain period of time, the betatron oscillations are attenuated and the beam size becomes small, and then the kicker magnet 620 again distorts the closed orbit to suit the injection, and the septum magnet 610 causes the electron beam from the accelerator to enter. This operation is repeated until a predetermined beam current is accumulated.

The accumulated electron beam has a Gaussian distribution.

The standard deviation of the electron beam size in the X direction and the Z direction can be expressed by the missing equations (1) and (2), respectively. However, x, z, and s are in the directions shown in FIG.

σ, = Vπ)〒ΣT ・・・・・・・・・(1) However, β8. β is called a betatron function in the X direction and two directions, respectively, and is a function of the position S on the electron orbit. η is a function called an energy dispersion function. E is the energy of the electron, and σ is the dispersion of the electron energy.

ε8. ε is a quantity called emittance in the X direction and two directions, and takes a constant value regardless of the position S. Therefore, the beam size in the X direction becomes large wherever the betatron function β and energy dispersion function η are large. In the two directions, the larger the betatron function β, the larger the beam size.

The betatron function is a function determined by the shape and strength of the deflecting and focusing electromagnet. The case where a normal conducting magnet and a superconducting magnet are used as this deflecting and focusing electromagnet will be explained respectively.

FIG. 1 is a perspective view showing the state in which the present invention is applied to a normal conducting magnet. In this embodiment, four polarizing magnets 601 are installed for one set of radiating devices, and each of them shares the polarizing action of 90°.

It is said that the wavelength of the synchrotron radiation required for lithography is around 15 nm. Therefore, the peak wavelength of the synchrotron radiation is set to 15 people. At this time, the relationship between the magnetic field strength B of the deflecting and focusing electromagnet and the electron energy E is expressed by the following equation (3).

0.935 Part B (3) Therefore, if the magnetic field strength is 1.2T, the electron energy will be 0.883GeV.

A normal conducting magnet 601 has a C-shaped iron core 130 and a coil 1.
It's 40 years old. The iron core of the magnet has a slope of the magnetic pole surface by a certain distance Lo from both ends, and the remaining part is ``row'' 6, slope 0.
'Hamacho Cup 5 Ugly 1100, name it Cl2O, and name the parallel part B110.

A vertical cross section of the A100 section is shown in FIG. 4, a vertical cross section of the B110 section is shown in FIG. 5, a vertical cross section of the Cl2O section is shown in FIG.
Each is shown below. These 4th. 5. In FIG. 6, the right side of the figure corresponds to the outside of the rotation trajectory of the electrons.

The above-mentioned section A 100 has a structure in which the magnetic pole face 150 opens outward so that the magnetic field strength becomes weaker on the outside. 0
Contrary to the above, the portion 120 has a structure in which the magnetic pole face 160 is open on the inside so that the magnetic field strength on the inside becomes weaker. Therefore A
In section 100, it is the X direction.

The beams converge in both directions. On the other hand, in the C section 120, the X direction converges, but the two directions diverge.

The magnetic pole spacing of the parallel part B110 is d, and the length of the iron core 130 is t.
1 The relative permeability of the iron core is μ, the coil current is μ, and the number of turns is N.
Then, the magnetomotive force NI and B, d.

The following relationship exists between t and μ.

The magnetic pole spacing d of the normal conduction magnet (Fig. 1) of this example is 10c.
m, the horizontal length of mJFl is 20m, the height of the magnet is 70cm, the width is 50an, and the average length of the iron core is 53crr.
1. The effective length in the orbit direction is 385 crn. A part 10
The effective length t in the orbit direction of 0 is 30crn1C part 120
The effective length t1 in the orbital direction is 30 crn. Since the relative magnetic permeability of the iron core is about 2000, the magnetomotive force from equation (4) is expressed by the following equation (5).

NI=9.6X10' (A-T) ・・・・・・
(5) Define n, which is calculated by formula (6), using the change in the magnetic field strength of parts A and B as the calculation amount.

p-dB ・・・・・・・・・(6) d
x If nt-na of part A and n of part B are rlj, then na.

By adjusting the value of n-, the υ electron stably moves into a closed orbit40
It revolves around 0 while making an oscillating motion.

FIG. 10 shows the stable region of the trajectory when the length of the straight section shown in FIG. 3 is 1.7 m. The portion below the curve a is a stable region of motion in two directions, and the portion surrounded by curve C2d is a stable region of motion in the X direction. Therefore, the stable region 900 in both directions is indicated by parallel hatching. One point (n, .

n)) to determine the operating point of the storage ring. n1=15
, 1b=io as the operating point, the betatron function in the B=1.2 direction is as shown in FIG.

If the emittance ε8 is 5X10-' (mRad), the beam size is maximum at σmaaax"1.
It will be 7cm. The electron beam has a Gaussian distribution and has a shape 1220 shown in FIG. Therefore, the radiation light emitted from the electron beam also has a Gaussian distribution 1230. Again-
Even when electrons emit synchrotron radiation, the emission direction has a probability distribution, and the half-width is given by the following equation (7).

However, r = E / mo C, which is the ratio of electron energy to rest mass. Therefore, the distribution at a point a certain distance from the light emitting point is also the distribution 123 as shown in Figure 12.
It becomes 0. When radiating radiation onto the wafer 820 (FIG. 9), it is desirable that the intensity of the radiation be uniform. Therefore, both ends of the emitted light distribution 1230 are cut off by a sulin 1240 (FIG. 12). Assuming that the cutting position is the position where the intensity of the emitted light becomes 1/2, the effective size S of the electron beam visible from the wafer side is 2.4σ. FIG. 13 shows the electron beam size S. At the point where the beam size is maximum, Sg+max! It will be 4crn.

At a point distant from the light emitting point 1200, formula (7)
This is the sum of the spread of the synchrotron radiation and the spread of the electron beam. Therefore, the irradiation height H is expressed by the following formula (8)
Hail to you.

H=χL+2.4σ,,,□・・・・・・・・・
- (8) Since E = 0.883 GeV, z = 0.74 milliradian from equation (7). Therefore L=
A mask 800 and a wafer 82 shown in FIG. 9 are placed at a 5 m point.
If 0 is installed, the height of the irradiation will be 4.5 cm.

Next, an example using a superconducting magnet will be described. If the magnetic field strength of the superconducting magnet is 4T, then equation (3)
The energy of 1υ electron is 0.48306V.

The deflection magnet is of a four-segmented type, as in the case of the normal conduction magnet in the previous embodiment, and one deflection angle is 90°.

FIG. 14 shows a superconducting magnet, where 260 is an iron core and 240 is a superconducting coil. FIG. 15 shows a vertical section of section A' in FIG. 14, and FIG. 16 shows a vertical section of section 07 in FIG.

650 is a vacuum chamber through which the electron beam passes, 230
240 is a radiation shield, 240 is a superconducting coil, 250 is a cooling helium container, 260 is an iron core, and 270 is a vacuum container. The iron core 260 has a shape in which the vacuum chamber 650 is sandwiched in the vertical direction.

The distance t from the orbital plane of the electron beam to the center of the coil is 6.6 cm, and the vacuum chamber diameter d is LO cm.

The inner diameter of the liquid helium container is 11 Cm1, and the outer diameter is 37 crr.
1. The inner diameter of the vacuum vessel is 150z, and the effective length in the orbital direction is t.

is 0.63m. At this time, the coil magnetomotive force is approximately 1.3
X10' (A-T), current density is 260 (A/f1
2).

A plan view of the superconducting coil 240 is shown in FIG. 17, and a side view is shown in FIG. 18. FIG. 19 is a sectional view taken along line II in FIG. 18, and FIG. 20 is a sectional view taken along line II of FIG. 18.

A' 200 from point U to point 7 of the coil, W from point V
B'200 from the point to the point, C'220 from the W point to the X point,
Two points i from point Y are named D'300.

The upper and lower coil spacing at A' section 200 is 07 section 22
The coil spacing at 0, the coil spacing at the 82 section 210 is h-1, and the coil spacing at the D' section is h. h,hb
, h, , ha satisfy the following relationship.

h, > h, = J : > h, ...
(9) At this time, in the A' part 200, the magnetic field strength on the outside is weaker than on the inside, and in the 07 part 220, on the contrary, the outside magnetic field strength is stronger than the inside, and the magnetic field strength in the 82 part 210 is constant. . Therefore, as in the case of a normal conducting magnet, A' part 2
At 00, both the x and z directions converge, and at 07 section 220, the X direction converges, and the two directions diverge. As in the case of a normal conducting magnet, if n at part A' is N, and n t N b at part C', and the length of the straight part is 0.5 m, the stable region of the orbit is the second
This corresponds to the shaded area 1300 in FIG. Set the operating point to N, = 6, Nb
=3 In this case, the betatron function in two directions becomes as shown in FIG. Emittance εm wo5X10-'mR,e
d, the beam size S1 becomes as shown in FIG. The area from point 3 to point t is the area where synchrotron radiation is generated. At the point where the beam size is maximum, σ@va*x=0.87on
It is.

Therefore, the half width of the beam is 2 crn.

As mentioned above, the energy of the electron is 0.483 GeV, so γ = 966, and the spread of synchrotron radiation ψ is 1.4.
It becomes milliradian. Therefore, the irradiation height H at a point 5 m from the light emitting point is 29 Iyr& from equation (8).

〔Effect of the invention〕

As described in detail above, by applying the present invention, one part of the deflection magnet of a synchrotron radiation irradiation device is provided with a part that performs the electron beam deflection action and the focusing action, and the other part is provided with a part that performs the electron beam deflection action and the electron beam focusing action. A simple configuration can be achieved by providing a part that performs the beam deflection action and the divergence action, and by configuring it to perform only the deflection action of the other partially expanded electron beams, and omitting the installation of a magnet dedicated to convergence and a magnet dedicated to divergence. This has the excellent practical effect of enlarging the size of the synchrotron radiation emitted from the electron beam, and greatly contributes to the development of compact synchrotron radiation irradiation equipment with a large exposure area.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a normal conducting magnet in an embodiment of the synchrotron radiation irradiation apparatus of the present invention. FIG. 2 is an overall view of the fine pattern transfer device, and FIG. 3 is a front view of the electron storage ring. 4 is a sectional view of section A of the normal conduction magnet shown in FIG. 1, FIG. 5 is a sectional view of section B, and FIG. 6 is a sectional view of section C. FIG. 7 is a plan view of a beam line that guides a synchrotron radiation beam to a semiconductor wafer, and FIG. 8 is a front view of the same. Figure 9 is a schematic diagram of the installation station where semiconductor wafers are installed, Figure 10 is a diagram showing the stability area of the storage ring when a normal conducting magnet is used, and Figure 11 is the operating point in the stability area of Figure 10. is na=15. It is a chart showing a betatron function when n4=10. Figure 12 shows the relationship between the electron beam size at the emission point and the vertical spread H of synchrotron radiation at a point L away from the emission point, and Figure 13 shows the relationship between the electron beam size at the emission point and the vertical spread H of the synchrotron radiation at a point L away from the emission point. 2 is a chart showing the electron beam size of . Fig. 14 is a front view of a superconducting magnet in a different embodiment from the above, and Fig. 15 is A of Fig. 14.
FIG. 16 is a schematic diagram showing a cross section of the <07 section. FIG. 17 is a plan view of the superconducting coil in the embodiment shown in FIG. 14, and FIG. 18 is a side view of the same. FIG. 19 is a schematic diagram showing the 1-1 section analysis plane of FIG. 18, and FIG. 20 is a schematic diagram showing the U--U cross section. FIG. 21 is a chart showing the stability region of the storage ring when using a superconducting magnet, and FIG. 22 is a chart showing the stability region of FIG. 21 with the operating point n, = 6. FIG. 23 is a chart showing the betatron function when nb = 3. FIG. 23 is a chart showing the electron beam size at each point on the electron beam trajectory. Second
Figure 4 is a schematic diagram showing the expansion of synchrotron radiation. 100... Slanted part of the magnetic pole surface, 110...
Portion where the magnetic pole surface is parallel, 120... Portion where the magnetic pole surface is inclined, 130... Iron core, 140... Coil, 15
0...Magnetic pole spread outward, 160...Magnetic pole spread inward, 170...Parallel magnetic pole, 200...
A part where the distance between the upper and lower coils is wider, 210...A part where the distance between the upper and lower coils is the average distance between a wider part and a narrower part, 220... A part where the upper and lower coil intervals are narrower, 230...Radiation shield, 240
...Superconducting coil, 250...Helium container, 26
0... Iron core, 270... Vacuum vessel, 400... Closed electron orbit, 500... Accelerator, 510... Storage ring, 520... Beam line, 530... Installation station, 600 ...Deflection and convergence electromagnet, 610...
・Septum magnet, 620... Kitzker magnet, 630・
-・High frequency acceleration cavity, 640...Beam monitor, 7
00...Absorber, 710...Shutoff pulp, 72
0... Beam shutter, 800... Mask, 810
...Resist, 820...Semiconductor wafer, 900.
... Stable region, 1200... Luminous point, 1210...
Point distanced from the light emitting point, 1220...Electron beam shape, 1230...Synchronized light beam shape, 124
0...Slit, 1300...Stable area, A...
The part of a normal conduction deflection magnet where the magnetic pole face is sloped so that the magnetic field strength is weaker on the outside, B... The part of a normal conduction deflection magnet where the magnetic pole faces are parallel, C... The part of a normal conduction deflection magnet The part where the magnetic pole face is sloped so that the magnetic field strength is stronger on the outside,
A'...The part of the superconducting deflection magnet where the distance between the upper and lower coils is widened so that the magnetic field strength is weakened on the outside, B'...
In a superconducting deflection magnet, the spacing between the upper and lower coils is between A' and C', C'... In a superconducting deflection magnet, the spacing between the upper and lower coils is narrowed so that the magnetic field strength is stronger on the outside. The part D' is a superconducting deflection magnet, and the upper and lower coil spacing is between A' and C'.

Claims (1)

[Scope of Claims] 1. An electron storage ring having a high-frequency acceleration cavity for accelerating electrons, a magnet for deflecting the electron beam, a magnet for focusing the electron beam, a magnet for diverging the electron beam, and a vacuum chamber, and an installation for installing an object to be irradiated. In a synchrotron radiation irradiation apparatus that includes a station and a beam line that guides synchrotron radiation from the synchrotron radiation generation point of the electron storage ring to the object to be irradiated, the electron beam deflection magnet has a part thereof that deflects the electron beam. A part is provided that performs a converging action and a part that performs an electron beam deflection action, and another part is provided that performs an electron beam deflection action and a diverging action, and the other part is configured to perform only an electron beam deflection action. ,
A synchrotron radiation irradiation device characterized by omitting the installation of a magnet dedicated to convergence and a magnet dedicated to divergence. 2. The electron beam deflection magnet described above is a normal conducting magnet having an iron core and a coil, and the portion that performs the deflection action and divergence action has a shape in which the distance between the magnetic poles is narrowed toward the outside in the radial direction. In addition, the portion that performs the deflection action and the divergence action has a shape in which the magnetic pole spacing is widened toward the outside in the radial direction, and the magnetic pole spacing in other portions is made equal. The synchrotron radiation irradiation device according to item 1. 3. The electron beam deflection magnet described above is a superconducting magnet consisting of an iron core and a superconducting coil, and the coils that perform the deflection and divergence functions are arranged so that the outer coil spacing in the radial direction is Claim 1, characterized in that the spacing between the coils is narrower than the spacing between the coils, and the spacing between the outer coils in the radial direction is wider than the spacing between the coils on the inner side of the coils in the portions that perform the deflection action and the convergence action. The synchrotron radiation irradiation device described in 2.